Electric blanket shell and method of production

ABSTRACT

An electric blanket shell is composed of first and second-needled textile fabrics with a yarn layer disposed in at least one of the needled fabrics. The yarn layer has a plurality of first planar yarns extending generally in a first planar direction. A heat-fusible component is disposed in at least one of the needled fabrics. A plurality of small, discrete sonically or ultra-sonically-produced fusion bonds, spaced from each other, link the needled fabrics to form a blanket shell. The fusion bonds form a series of patterns across a planar dimension of the blanket shell and the patterns define a series of channels, for receiving heating wires, between the needled fabrics. The patterns of fusion bonds are disposed in a direction transverse to the direction of the first planar yarns. The fusion bonds of any one pattern do not engage more than about 50% of the first planar yarns and overlaps of fusion-bond patterns are substantially avoided.

ELECTRIC BLANKET SHELL AND METHOD OF PRODUCTION

The present invention is concerned with electric blanket shells whichare produced from needled textile fabrics.

BACKGROUND OF THE INVENTION

Electric blanket shells must have spaced channels between the shellfabrics to receive electrical heating wires. These channels position theelectrical heating wires and, accordingly, must be uniformly disposedacross the length and width of the blanket shell (except at the top,bottom and sides thereof) in order to produce a uniform heating effect.On the other hand, the channels must prevent contact of adjacent wiresor even close proximity thereof, since dangerous localized overheatingmay otherwise occur. Thus, the shell fabrics must be joined in anaccurate and positive manner.

Woven blanket shells might be produced by weaving shell fabrics andsewing the fabrics halves together with conventional thread sewing toform these channels, but this technique would involve considerable handlabor to accurately sew the channels and insure continuous, unbrokenstitching. Such a technique has never been economical. The conventionaltechnique of forming the channels for electric blanket shells is by aspecial weaving technique. In effect, the two shell fabrics are woven atone time on a single loom with a pattern of common warp yarns which joinor lash the two shell fabrics at spaced intervals to form the channels.While this technique provides a very predictable pattern of channels andis most positive in joining the shell fabrics, it does involve therelatively slow weaving process.

Needed blankets (i.e., non-woven) have the essential strength and wearcharacteristics of woven blankets, and the needling technique canproduce blankets at rates of 30 to 50 times faster than the weavingprocess. However, the needling technique cannot form channels, as canthe special weaving technique. Thus, if electric blanket shells are madeof needled fabrics, the needled fabrics must be joined so as to formchannels with accuracy and positiveness for the same reasons notedabove. Also, the practical thickness of conventional needled fabrics isgreater than that of woven fabrics and the resulting total thickness ofa needled fabric blanket shell is too great for comform in use. In viewof the foregoing, needled fabrics have not been practical for producingelectric blanket shells.

In view of the much greater production speed of needled fabrics, itwould, of course, be most desirable to provide means of accurately andpositively joining needled fabrics to produce channels for an electricblanket shell. In this regard, it is known that non-woven fabrics may bejoined by adhesion bonding, i.e., the application of glues, or by fusionbonding, i.e., the application of heat as by hot gas, flame andconduction (e.g., a heated iron). Fusion bonding considerably reducesthe strength and fibrous nature of the fabric in the vicinity of thefusion bond, and while adhesion bonding preserves the strength andfibrous nature of the fabric, the practical problems of handling gluesmake it difficult to accurately, predictably and positively join suchfabrics.

An alternative means of heating to cause fusion bonding is broadly knownas vibrational heating. This technique involves the creation of arelatively high frequency vibration in a driver and this vibration isdirected by a horn in physical association with the driver to localizedparts of the substrate to be heated. A rigid element, called an anvil,is disposed on the opposite side of the substrate and vibrations inducedin the substrate cause frictional heating. This vibrational energy canbe in either the sonic or ultra-sonic frequency ranges. The techniquehas the advantage that the heat produced can be closely controlled andcan produce predictable and localized heating. Vibrational heating hasbeen used to weld thermoplastic sheets together. Localized heating ofthe sheets of thermoplastic along a narrow, relatively continuous bandcauses the thermoplastic sheets to be melted and then resolidifiedtogether.

This process works well with relatively high density, homogeneous, solidsubstrates, such as plastic sheets, because the welded (melted andresolidified) substrates are essentially the same as unwelded substratesin regard to the character and properties. However, with relatively lowdensity, non-homogeneous substrates, such as textile fabrics, theprocess presents serious problems. A textile is considered to benon-homogeneous and relatively low density material in that it containsa large percent of voids between fibers.

It can be appreciated that a textile derives much of its character andphysical properties from the spatial configuration of the fibers and theinteraction between fibers, while a plastic sheet derives much of itscharacter and physical properties simply from the mass of the plastictherein. Thus, contrary to welding plastic sheets, any melting of fibersin a textile fabric tends to severely reduce the basic character andphysical properties of fibers adjacent to a fusion bond. Nevertheless,vibrational heating has been used to bond textile fabrics and thistechnique has been referred to as sonic or ultra-sonic sewing orseaming, although the method really involves fusion bonding.Conventional apparatus and methods of such sewing and seaming areillustrated in U.S. Pat. No. 3,666,599, issued May 30, 1972, and U.S.Pat. No. 3,734,805, issued May 22, 1973. The technique can also be usedfor placing patterns on textile materials, and U.S. Pat. No. 3,733,238,issued on May 15, 1973, is representative of that art. Since this art iswell known, the details of the apparatus and the methods will not berepeated herein and the aforenoted U.S. patents are incorporated hereinby reference and relied upon for those known details.

As noted above, the localized heating produced by the vibrational energycauses fusion of the fibers of the textile fabric and this fusion actionalters the molecular structure of the fibers and therefore degrades thephysical properties and character of the fibers in and adjacent to thefusion area. Under the circumstances, localized weakening of the bondedfabric takes place in and around fusion bonds. When a pattern of suchfusion bonds exists across a dimension of a bonded fabric, then thatpattern will tend to form a corresponding pattern of weakened areas.More specifically, a pattern of fusion bonds may define a weakened lineor "tear-line" in the plane of the fabric. In woven textile fabrics,this undesired "tear-line" effect is somewhat mitigated by the verynature of the woven fabric itself. Thus, the tight, twisted arrangementof fibers within the yarns making up a woven fabric produces anextremely high degree of interfiber friction. Additionally, thesystematic arrangement of these twisted yarns making up the warp andfilling of the woven fabric, along with the interfiber friction of thetwisted yarns, produces a very high degree of fabric integrity. Thishigh degree of integrity is such that even if many of the fibers, oreven yarns, are substantially degraded by the fusion bonding, theremaining interfiber friction and systematic arrangement still providequite high fabric integrity and, correspondingly, the strength of thefabric which remains is sufficient for many purposes.

In contrast, the fiber arrangement in a needled fabric is far morerandom rather than systematic, i.e., as compared with the twisted andprecise pattern of a woven fabric. Such arrangement is, therefore, lessefficient in producing interfiber friction. The needling process resultsin a complex fiber entanglement which give rise to the interfiberfriction of a needled fabric and if this entanglement is degraded in abonding operation, the essential strength providing feature of theneedled fabric is seriously degraded. Thus, when a pattern of fusionareas exist across a dimension of needled fabrics, then that patternwill tend to form a corresponding pattern of pronounced weakened areasand the "tear-line" effect becomes most serious. As a result of theforegoing, sonic or ultra-sonic bonding of needled textile fabrics hasnot been generally accepted where the bonded fabric must provide astrong joint and can not exhibit a "tear-line" effect.

It would, however, be most advantageous to provide a method of fusionbonding needled textile fabrics to form electric blanket shells whereinthe foregoing difficulties are essentially obviated.

OBJECTS OF THE INVENTION

It is therefore an object of the invention to provide electric blanketshells where needled textile fabrics are fusion bonded together in sucha manner as to avoid the difficulties noted above. It is yet a furtherobject to provide such electric blanket shells which allow patterns offusion bonds across a dimension of the shell and which yet provide ahigh level of confidence in the bond strength of the shell andessentially avoid a "tear-line" effect. Other objects will be apparentfrom the following disclosure and claims.

BRIEF DESCRIPTION OF THE INVENTION

Briefly stated, the present invention is based on the discovery thatneedled fabrics may be vibrationally fusion bonded, e.g., sonic orultra-sonically bonded, in such a manner that patterns of fusion bondsmay extend across a dimension of the bonded fabrics and yet avoidweaknesses thereacross, wherein: (1) at least one of the needled fabricshas therein a layer of yarns (including annexed to and therebetween)with at least some of the yarns extending traversely of the pattern offusion bonds; (2) individual fusion bonds are spaced apart and any onepattern of fusion bonds engages no more than about 50 percent of thetransversely extending yarns; and (3) the fusion bonds of one pattern donot substantially overlap with the fusion bonds in a closely adjacentpattern. The traversely disposed yarns will disrupt any "tear-line" or"tear-strip" effect and avoid the weakness which would otherwise developin a pattern of fusion bonds across a dimension of the shell.

Thus, the present invention provides an electric blanket shellcomprising a first and a second needled textile fabric which aredisposed in juxtaposition to each other and each fabric has the textilefibers needled together into an integral, coherent structure. A yarnlayer is disposed in at least one of the first and second fabrics(including annexed to and therebetween) and that yarn layer has aplurality of first yarns extending generally in a planar dimension ofthe needled fabric. A heat fusible component is disposed in at least oneof the first or the second needled fabrics (including annexed to andtherebetween) and a plurality of small, discrete fusion bonds (i.e.,sonic or ultra-sonic fusion bonds), spaced from each other, link thefirst needled fabric to the second needled fabric to form a blanketshell with a series of patterns which extend across a dimension of theblanket shell. The patterns of fusion bonds define a series of channelsbetween the first and second needled fabrics. The patterns of fusionbonds are disposed in directions which are traverse to the direction ofthe first planar yarns of the yarn layer. Where the yarn layer is usedin both needled fabrics, the first planar yarns of both fabrics aregenerally parallel to each other. The fusion bonds, however, arearranged so and spaced so that the fusion bonds of any one traverselyextending pattern do not engage more than about 50 percent of the firstplanar yarns and so that overlaps of fusion bond patterns aresubstantially avoided.

Preferably both the first and second needled fabrics contain both theyarn layer and the heat fusible component. The heat fusible componentmay be a thermoplastic or thermosetting polymer, preferably in fibrousform. Indeed, the needled fabrics may be of only fusible fibers and allof the fibers thereof can, therefore, function as the fusible component.Alternately, of course, the needled fabrics can be made of a mixture offibers where one of the fibers has a lower softening or melting pointand therefore functions as the fusible component.

The planar yarn layer may be a self-supporting layer or not and may takevarious forms. Thus, the layer may be simply a series of conventionalcarrier yarn which will not be self-supporting or it may be a spunbonded or woven scrim or the like, which is self-supporting. In each ofthese latter two cases, of course, there will also be significantnumbers of yarns which will extend both essentially traversely andparallel to the patterns of fusion bonds. For example, where a wovenscrim is used the wrap yarns thereof may form the first planar yarns andthe filling will form second planar yarns which are also generallyparallel to the pattern of fusion bonds. Of course, with non-woven spunbonded scrims the first planar yarns may be any of the yarns whichextend generally in one dimension (or direction).

The yarns may be elongatable yarns, i.e., capable of being stretched andin the preferred embodiment of the invention, the needled fabrics withthe yarn layers therein are stretched and set prior to forming the shellso as to reduce the thickness, and hence the weight per unit area, ofthe needled textile fabrics from which the shell is made.

Each fusion bond will generally have a planar dimension no greater than0.75 inch, although smaller planar dimensions are preferred. In anyevent, there will be no substantial numbers of closely adjacent fusionbonds, in any one pattern, which overlap. This further avoids a"tear-strip" effect.

According to the method of the invention, the electric blanket shell ismade by needling first and second batts of textile fibers into needledfabrics having an integral coherent structure, wherein after needling atleast one of the first and second needled fabrics contains the heatfusible component and at least one of the first and second fabricscontains the planar yarn layer having a plurality of first planar yarns(or the fusible component and/or yarn layer is annexed to at least onefabric or between two fabrics). The first planar yarns extend generallyin a first planar dimension of the needled fabric. After these first andsecond fabrics are placed in layered juxtaposition (one laid on top ofthe other), a plurality of small discrete fusion bonds, spaced from eachother, are formed so as to link the first fabric to the second needledfabric. These fusion bonds form at least one pattern of bonds whichextends across a dimension of the blanket shell but wherein the patternsof fusion bonds do not engage more than 50 percent of the said firstplanar yarns which traverse the pattern of fusion bonds. The fusionbonds are also disposed traversely across the first planar yarns so thatoverlaps of fusion bond patterns are substantially avoided. Normally,the fusion bonds are formed by moving the combination of the first andsecond needled fabrics with the fusible component and planar yarn layerpast a bonding station (sonic or ultra-sonic) which successively formsbonds in the pre-set pattern.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 shows a typical pattern of fusion bonds and resulting channelsfor an electric blanket shell.

FIG. 2 is a fragmented top view of a shell which is fusion bonded withpatterns of fusion bonds extending transversely across the composite.

FIG. 3 is a diagrammatic illustration of a cross-section of the shell ofFIG. 2, the cross-section being taken along A/A of FIG. 2.

FIG. 4 is a highly idealized diagrammatic illustration of patterns offusion bonds which engage longitudinally extending spun yarns within theshell.

FIG. 5 is a diagrammatic illustration of apparatus for stretchingneedled textile fabrics from which the present shells are made.

FIG. 6 is a diagrammatic illustration of apparatus suitable forproducing fusion bonds in the present shell.

DETAILED DESCRIPTION OF THE DRAWINGS

In FIGS. 1 and 2, the shell 1 has a pattern 2 of fusion bonds 3. Thelongitudinal direction 4 will usually be in the machine direction of theneedled fabrics used in forming the shell. The fusion bonds 3 are shownas dashes in FIG. 1 and as circular dots in FIG. 2. However, theparticular pattern 2 is not narrowly critical and the pattern of thefusion bonds may take many and varied forms. FIG. 1 is representative ofa suitable form with electric wire channels 5 between patterns of fusionbonds. Also, the configuration of the fusion bonds or the shape of thepattern of bonds may vary widely, as illustrated by patterns 6 through11 of FIG. 2. Thus, the fusion bonds may be relatively large but furtherspaced apart, as shown in pattern 6 or relatively small and more closelyspaced, as shown in pattern 7. Alternately, the fusion bonds may beelongated in a transverse direction as shown by pattern 8 or in thelongitudinal direction, wholly or in part, as shown in pattern 9. Or thefusion bonds may vary within a pattern or within a combination ofpatterns as shown by patterns 10 and 11.

As shown in FIG. 3, the fusion bonds 20 pass through the thickness 21 tolink together the first needled fabric 22 to the second needled fabric23. Only one of the fabrics i.e., fabric 22 may have the yarn layer 24therein, as shown on the A portion of FIG. 3, or both fabrics 25 and 26may have the yarn layers 27 and 28, respectively, as shown in the Bportion of FIG. 3 therein. This latter embodiment is the preferredembodiment. Alternately, the yarn layer may be annexed to an alreadyformed needled fabric, e.g., by lightly glueing, stitching, bonding,etc. or simply laid between two already formed needled fabrics. Or theneedled fabrics may be needled from a web a fibers laid on the yarnlayer in such a manner that the yarn layer is not needled into theneedled fabric. These latter embodiments, however, are not preferred.Nevertheless, for purposes of the present specification and claims theterm "disposed in", with regard to the yarn layer and needled fabric isdefined to include the yarn layer annexed to a needled fabric or laidbetween needled fabrics.

In the highly idealized illustration of FIG. 4, it is shown that thefusion bonds 30 should not engage more than 50 percent of the planaryarns 31 which traverse the pattern 32 of fusion bonds. Thus, thepattern of fusion bonds 33 would engage too may planar yarns and would,thus, not be acceptable for the present invention. Even smaller bondsbut too closely spaced, such as fusion bonds 34, will engage too manyplanar yarns and would not be satisfactory for the present invention.Alternately, even though the fusion bonds are spaced apart, ifsubstantial number of fusion bonds in any one pattern overlap too manyclosely adjacent fusion bonds, as bonds 35, then too many yarns would beengaged by closely adjacent fusion bonds in a pattern and will not beacceptable for the invention. The pattern of fusion bonds 36 isrepresentative of a preferred pattern and relative proportion of fusionbonds.

Of course, the fusion bonds need not traverse the pattern of fusionbonds in only perpendicular or transverse direction but the bonds maytraverse the pattern of bonds in an oblique manner, as illustrated byarrow 37 or even in a zig-zag or in a sinuous or other similar pattern,as illustrated by arrow 38.

As noted above, in an electric blanket shell, if the total shellthickness is too great, then the blanket will be unduly warm for theuser even without the use of the electrical resistence wires foradditional heating. Thus, if the individual needled fabrics arerelatively thick, then when made into a layered shell, the total shellwill be too thick for comfort of the user. It is, however, extremelydifficult to make needled textile fabrics such that the thickness of twolayers thereof is within acceptable ranges for electric blanket use.According to another important feature of the present invention,therefore, at least one of the needled textile fabrics is longitudinallystretched, prior to being formed into the shell, to reduce the thicknessthereof. When the planar yarns are in the needled fabrics to bestretched, the planar yarns will also have to be stretched whenstretching in the said first dimension of the meedled fabric. Thus, forstretching of this embodiment the planar yarns in the first needledfabric dimension must be elongatable, that is, they must be permanentlyelongatable under tension, with or without heat or solvent action, e.g.steaming, etc., during the stretching operation.

Suitably, the stretching can be accomplished in a conventional apparatusas diagrammatically illustrated in FIG. 5 where the needled textilefabric 40 passes through a heated chamber 41 and is stretched betweenthe set of nip rolls 42 and the set of nip rolls 43. This stretchingreduces the thickness from T₁ to T₂. The unit elongation between thesets of nip rolls 42 and 43 is generally at least 10% and usually atleast 15-25%. Unit elongations up to 50% may be used.

The stretching operation is not critical in terms of the specificdetails and conditions. Thus, any of the known and generally practicedstretching methods and conditions may be used. However, if heat is usedin stretching then the temperature of the needled fabric should notexceed the melting point of any component therein, since it is notdesired that the needled fabric be in any way fused at this stage of theprocess. Suitable stretching apparatus, processes and techniques arefully described in U.S. Pat. No. 3,154,462, which is incorporated hereinby reference.

The pattern of fusion bonds may be made by an apparatus as illustratedin FIG. 6. This figure illustrates the use of either sonic orultra-sonic energy for accomplishing the fusion bonding. Irrespective ofthe frequencies, e.g., sonic or ultra-sonic, energy is produced by wayof a conventional driver 50 and directed to the fabric by way of aconventional horn 51. The layers of needled fabric 52 and 53 passbetween horn 51 and a driven roll 54. Carried on that roll is a seriesof projections 55 which form conventional anvils (normal gaps betweenthe horn and the anvil are in the range of 0.001 to 0.01 inch), as wellunderstood in the sonic and ultra-sonic welding art. These projectionsare in the same pattern as that desired for the fusion bonds 56 toproduce blanket shell 57. Of course, the apparatus will have associatedtherewith conventional controls 58 and a suitable power supply 59(allowing frequencies of between 12K Hertz and 40K Hertz). The detailsof apparatus of the foregoing nature are well known in the art and theaforementioned U.S. patents provided those details.

While the invention can be satisfactorily practiced with no more thanabout 50 percent of the yarns being engaged by fusion bonds, it ispreferable that no more than about 40 percent, e.g., no more than about30 percent, of the yarns traversing the pattern of fusion bonds beengaged by the fusion bonds. Of course, if the yarns have a meltingpoint substantially higher than the fusible component in the needledfabric, then the fusion bonding may be accomplished at lowertemperatures and, accordingly, have less deleterious effect on theyarns. In this case, the proportion of yarns which may be engaged by thefusion bonds and yet produce satisfactory results will be toward theupper limit of the foregoing range. On the other hand, when the yarnshave melting points close to the melting points of the fusion component,then the lower portion of the foregoing range is preferred.

As noted above, it is preferred that both the first and second needledfabrics contain the heat fusible component. This insures good fusionbonding throughout. However, similar to the planar yarn layer thefusible component may be annexed to a needled fabric or laid betweenneedled fabrics and it is likewise intended that the specification andclaims be so defined and construed. The fusible component may be eithera thermoplastic or a thermosetting polymer. In this latter regard, acatalyst or activating agent will normally be required to cause thefusion bonding of the thermosetting polymer. For example, some of thefibers in the composite may have a thin coating of a "b"-stage catalyzedepoxy resin and by the application of heat, the "b"-stage resin is curedto the "a"-stage resin and thus forms the fusion bond. whether thefusible component is thermoplastic or thermosetting, it is preferably infibrous form. That is to say, that the fusible component will either bea homogeneous fiber itself or will be associated with a fiber. Forexample, the fusible component may be one of the discrete components ofa multi-component fiber. One component of a fiber may be a strengthproviding component, such as a nylon fiber, while the other componentmay be a lower melting point fusible component such as a polyvinylchloride. alternately, such a multi-component fiber may have a coatingof the fusible component on the fiber and thus form concentriccomponents. In this case, of course, the fusible component is theoutermost component. Of course, the fusible component may be on a bi- ortri- or multi-component fiber and other components may be used for thedesired properties thereof.

However, it is preferable that the fusible component is in the form of ahomogeneous fiber, for the sake of simplicity and predictability ofoperation. The homogeneous fiber may make up the entire fiber content ofone or both of the needled fabrics or it may be in admixture with fibersof different compositions which have different melting points and do notenter into the fusion bonding process. In a simple case, all of thefibers of both needled fabrics may be of the same composition and formthe fusion component under the action of the heat induced by the sonicor ultra-sonic generator.

As can be appreciated from the foregoing, it is necessary to causefusion of fibers, that is, at least some welding or melting together ofthe fibers. The fusion point is that temperature at which the fibersbecome sufficiently tacky to coalesce or flow together when injuxtaposition to one another. The fusion point, however, is not criticaland may vary widely. The fusion point may be from as low as 180°F. to ashigh as 700°F., although generally fusion temperatures between 250° and500°, especially between 300° and 475°F. are preferred.

When the fusible component is only a portion of either one or both ofthe needled fabrics, either as a component of the fibers or as aseparate fiber, the fusible component on a weight basis, should be atleast 10 percent of the weight of the shell, preferably at least 40percent and generally at least 60 percent. This will insure that uniformand strong fusion bonds are obtained.

The materials from which the fusible component may be chosen can varywidely and are not critical. Normally, however, the fusible componentwill be either a thermosetting or a thermoplastic polymer.

Examples of suitable thermoplastic polymers are polymers of α-olefins,such as polyethylene, polypropylene and polybutene; vinyl polymers suchas vinyl chloride, vinyl acetate, vinyl butyral, styrene; acrylonitrite;butadiene; methyl methacrylate; vinylidene chloride; polyvinyl acetate;halogenated α-olefin polymers, such as chlorinated polyethylene;halogenated vinyl chloride polymers, such as chlorinated polyvinylchloride; condensation polymers such as linear polyesters, e.g.,polyethylene terephthalate; polyamides such as polycaprolactam,polyhexamethylene adipamides; polyphenylene oxides, polycarbonates;thermoplastic oxymethylene polymers; thermoplastic linear polyurethanes;and the thermoplastic derivatives of cellulose such as celluloseacetate, cellulose butyrate and mixed cellulosic esters, for examplecellulose acetate butyrate. Of course, copolymers of the foregoing maybe used.

Examples of thermosetting polymers that may be used are phenol-aldehyderesins, amine-formaldehyde resins, epoxy resins, polyester resins,thermosetting polyurethanes, and vulcanizable rubbers. The thermosettingresins will normally contain a hardening agent or catalyst.

The yarns of the yarn layer may be chosen from a wide variety ofmaterials and the particular properties thereof are not critical. Theyarns may be a continuous filament (single or multi-filament), eithertwisted or not, or a spun yarn. It is preferred that a spun yarn beused. A "yarn" is defined as being a continuous strand composed offibers or filaments. These yarns, running traverse to the pattern offusion bonds will disrupt any kind of "tear-strip" effect which wouldotherwise be occasioned by that pattern of bonds. The yarns, therefore,are critical to the success of the invention. On the other hand, theparticular materials of the yarn can be almost as desired and can bechosen from the polymers noted above or any other conventional textileyarns, including cotton, wool, flax and the like, when the needledfabrics need not be stretched. The number of yarns which traverse apattern of fusion bonds is not narrowly critical, but preferably, thereshould be at least two yarns in a blanket shell for each fusion bondforming the pattern. Preferably, there will be at least three,particularly four and most suitable five to eight yarns for each fusionbond of the pattern of bonds traversing the shell. Thus, for example,there may be approximately from 5 to 50, especially 15 to 40, e.g., 30yarns per inch of the shell dimension traversing the pattern of fusionbonds. For example, in an 84 inch wide needled fabric, there may be from1400 to 2800 longitudinally extending yarns. The denier of the yarns,again, is not critical and conventional deniers may be used, e.g., from150 to 300 denier, especially from about 200 to 275 denier, e.g., 250denier.

In order to avoid undue engagement of the yarns by the fusion bonds, thefusion bonds should be no greater than 0.75 inch in any planardimension, especially no greater than 0.5 inch and especially no greaterthan an average of about 0.1 inch. By keeping the fusion bonds to theselower limits, it can be assured that no more than 50 percent of theyarns will be engaged by the fusion bonds. It should be specificallyunderstood that the fusion bonds should be relatively uniformly spacedapart such that there are no substantial numbers of closely adjacentfusion bonds, in any one pattern of bonds, which substantially overlapother bonds in the pattern. For example, it does no good to avoidengagement of more than 50 percent of the yarns by the fusion bonds whenthat 50 percent is in one-half of the shell. That one-half of the shellwould therefore be exceedingly weak. Neither should adjacent patterns beclosely spaced. Thus, no pattern of fusion bonds should be closer to thenext adjacent pattern of fusion bonds than the average distance betweenadjacent fusion bonds in one pattern. Thus, a substantial overlap ofpatterns is avoided.

The needled fabrics may be produced by any of the conventionaltechniques. Appropriate needling techniques are well known in the artand need not be described herein. However, U.S. Pat. Nos. 3,112,552,3,132,406, describe suitable needling techniques, apparatus and detailsand those U.S. patents are incorporated herein by reference for thatpurpose. Prior to the needling process, fibers are carded onto a beltand on top of the fibers the carrier yarns, scrim, etc. are placed andfurther fibers are carded thereonto. This web is then passed through aneedling machine which unites the fibers in the needling operation andforms a fabric of consolidated needled textile fibers. The needling maybe to the extent that coherent fiber entanglement occurs and especiallyto the extent and nature that "chain entanglement" occurs which has beenexplained in the above noted U.S. patents.

The amount of fibers underneath and above the yarn layer can varyconsiderably but it is preferred that the amount of fibers beneath theyarn layer be less than the amount of fibers above the yarn layer sothat the yarn layer of the fabrics (when used in both fabrics) is nearerthe center of the shell than the outer extremities thereof. In thisarrangement, the innermost layers may suitably contain the majority ofthe fusible component and thereby cause greater bonding near the centerof the shell. This arrangement will allow for a thicker top surfacewhich may be raised in a subsequent napping operation. Quite suitably,the lower-most layer can contain substantially all of the fusiblecomponent.

A pattern of fusion bonds will form channels between an adjacent patternof fusion bonds. These channels will terminate prior to reaching theedges of the shell and will allow for the normal electrical connectionsin producing a wired electric blanket from the shell. Of course, in thenormal manner either one or both of the surfaces of the shell may have anapped surface.

EXAMPLE 1

Two needled fabrics were produced by needling polyester staple fibersdisposed on acrylic carrier yarns. There were 1400 ends of twistedcarrier yarns (of approximately 200 denier each) across the needlingmachine width (needle board width) of approximately 85 inches. Theneedling machine was a FIBERWOVEN machine according to U.S. Pat. No.3,112,552. The needled fabric was stretched in a saturated steam box toprovide a stretched fabric of about 4.5 oz. per square yard (stretchedabout 20% on an area basis). The two needled fabrics were laid togetherwith the carrier yarns in each being parallel to each. A series ofpatterns of fusion bonds were made transversely of the carrier yarnswith a Branson model 200 ultra-sonic machine. The frequency of theelectrical driver was 20,000 hertz and the gap between the horn andanvil was 0.01 inch. The feed rate of the two needled fabrics throughthe machine was approximately 20 feet per minute. The pattern consistedmainly of sets of two parallel rows of small discrete, essentiallycircular, fusion bonds. The diameter of each fusion bond wasapproximately 0.035 inch and the center-to-center distance betweenfusion bonds was approximately 0.1 inch. The rows were approximately0.15 inch apart and the distance between sets of rows, forming thechannels for the electrical wires, was approximately 4 inches. Thechannels were well-formed and more than sufficiently strong and positiveto allow safe disposition of electrical heating wires.

EXAMPLE 2

Example 1 was repeated except that: the diameter of the fusion bonds wasapproximately 0.1 inch; the bonds were approximately 3/8 inch apart; therows of bonds in a set of rows were approximately 1/2 inch apart; andthe bonds in one row of the set of rows were parallel to but staggeredwith respect to the bonds in the other row. Satisfactory channels wereformed.

EXAMPLE 3

A bonded fabric similar to that of Example 1 was subjected to 25serially performed but separate washings in a home washing machine usingwarm water and Tide detergent with tumble drying. No substantialdeterioration of the fusion bonds could be detected.

Having thus described the invention and the preferred embodimentsthereof, it will be apparent to those skilled in the art that theinvention admits to many modifications and variations. Thesemodifications and variations are intended to be embraced by the annexedclaims.

What is Claimed is:
 1. An electric blanket shell comprising:1. first andsecond needled textile fabrics in juxtaposition to each other and eachfabric having textile fibers needled together into an integral, coherentstructure;
 2. a yarn layer disposed in at least one of the first andsecond needled fabrics and said yarn layer having a plurality of firstplanar yarns extending generally in a first planar dimension of theneedled fabric;
 3. a heat fusible component disposed in at least one ofthe first and second needled fabric;
 4. a plurality of small, discretefusion bonds spaced from each other which link the first needled fabricto the second needled fabric to form a blanket shell and a series ofpatterns across a planar dimension of the blanket shell which patternsdefine a series of channels between the first and second needledfabrics, said patterns of fusion bonds being disposed in a directiontraverse to the direction of the said first planar yarns of the yarnlayer; and wherein the fusion bonds of any one traversely extendingpattern do not engage more than about 50 percent of the said firstplanar yarns and wherein overlaps of fusion bond patterns aresubstantially avoided.
 2. The shell of claim 1 wherein both the firstneedled fabric and the second needled fabric contain the heat fusiblecomponent.
 3. The shell of claim 1 wherein the heat fusible component isthermoplastic or thermosetting polymer.
 4. The shell of claim 3 whereinthe fusible component is in fibrous form.
 5. The shell of claim 4wherein the fusible component is a discrete component of amulti-component fiber.
 6. The shell of claim 5 wherein themulti-component fiber is in the form of concentric components and thefusible component is the outermost component.
 7. The shell of claim 5wherein the fusible component is a component of a bi-component fiber. 8.The shell of claim 4 wherein the fusible component is in the form of ahomogeneous fiber.
 9. The shell of claim 8 wherein at least one of thefirst or second needled fabrics is a mixture of fibers of differentcompositions and the different compositions have different meltingpoints.
 10. The shell of claim 1 wherein both the first and secondneedling fabrics are composed of the same heat fusible fibers.
 11. Theshell of claim 1 wherein the yarn layer is a self-supporting layer. 12.The shell of claim 1 wherein the yarn layer also has a plurality ofyarns extending generally parallel to the pattern of fusion bonds. 13.The shell of claim 12 wherein the yarn layer is non-woven.
 14. The shellof claim 12 wherein the yarn layer is woven.
 15. The shell of claim 1wherein the yarns of the yarn layer are fusible.
 16. The shell of claim1 in which the needled fabrics are in an elongated condition.
 17. Theshell of claim 16 in which the elongated condition is at least 10percent greater than the non-elongated condition.
 18. The shell of claim1 wherein the fusion bonds have no planar dimension greater than 0.75inch.
 19. The shell of claim 1 wherein the fusion bonds have no planardimension greater than 0.50 inch.
 20. The shell of claim 1 wherein thefusion bonds have an average planar dimension no greater than 0.1 inch.21. The shell of claim 18 wherein no substantial numbers of adjacentfusion bonds, in any one pattern of fusion bonds, overlap.
 22. The shellof claim 21 wherein adjacent patterns of fusion bonds are no closer thanthe average distance between adjacent fusion bonds within a pattern. 23.The shell of claim 22 wherein at least one of the needled fabrics has atleast two layers and the innermost layer contains the majority of thefusible component.
 24. The shell of claim 23 wherein the innermost layercontains substantially all of the fusible component.
 25. The shell ofclaim 22 wherein the patterns of fusion bonds form channels betweenadjacent rows of fusion bonds.
 26. The shell of claim 25 wherein therows and channels terminate prior to the edges of the shell.
 27. Theshell of claim 26 wherein a complete pattern of rows of fusion bondsrepeats within distance intervals at least less than a blanket shellwidth.
 28. The shell of claim 1 wherein at least one surface of theblanket shell has a napped surface.
 29. The shell of claim 1 wherein thefusion bonds are sonic or ultra-sonic fusion bonds.
 30. The shell ofclaim 28 wherein the fusion bonds are ultra-sonic fusion bonds.